Dude, the show's over!

Keys are one of three collectibles available through the 20 missions. There are 21 Keys in total. After finding a collectible it will immediately be saved and you can return to the main menu. Some collectibles can only be reached by using certain abilities. Make sure to buy the "Leap" ability very early, it will come in handy.

IMPORTANT: You cannot get all collectibles on your first playthrough because certain weapons and abilities are required (which are unlocked automatically later in the game). After completing mission 10 you can replay all missions in the main menu and get missing collectibles.